The present disclosure relates to an optical film and a method for manufacturing the same, an antiglare film, a polarizer with an optical layer, and a display apparatus. In particular, it relates to an antiglare film used in a display surface of a display apparatus such as a liquid crystal display apparatus.
In display apparatuses (displays) such as liquid crystal display apparatuses, a technology is adopted in which an antiglare property is imparted and reflection due to surface reflection is reduced by providing antiglare films at the display surface side to diffuse light with the films. In conventional antiglare films, the antiglare property is imparted by an irregular shape provided on the surface thereof.
FIG. 1 shows the structure of a conventional antiglare film 101. As shown in FIG. 1, the antiglare film 101 includes a base member 111 and an antiglare layer 112 provided on the base member 111. The antiglare layer 112 contains fine particles 113. These fine particles 113 protrude from the surface of the antiglare layer 112, whereby an irregular shape is formed on the surface. This antiglare film 101 is formed by applying a coating material containing the fine particles 113 such as irregular-shaped silica fine particles or organic fine particles onto the base member 111 and drying the coating material. According to such an antiglare film having the above-described structure, the fine particles 113 protruding from the antiglare layer 112 scatter light incident on the antiglare layer 112, and thus reflection due to surface reflection is reduced.
Hitherto, investigations have been conducted on an irregular shape for effectively imparting the antiglare property to antiglare films. For example, Japanese Patent No. 3,821,956 has proposed that a center-line mean roughness and a mean peak-valley spacing of the irregular shape be selected from the range of 0.08 to 0.5 μm and the range of 20 to 80 μm, respectively, in order to prevent glare. In addition, Japanese Patent No. 3,374,299 has proposed that, in order to realize good antiglare property, rough irregularities and fine irregularities are provided in which the center-line mean roughness Ra and the mean spacing Sm of the surface having these irregularities thereon are controlled to 0.1 to 1.0 μm and 20 to 120 μm, respectively, the center-line mean roughness Ra and the mean spacing Sm of the rough irregularities are controlled to 0.5 to 1.5 μm and 100 to 300 μm, respectively, and the center-line mean roughness Ra and the mean spacing Sm of the fine irregularities are controlled to 0.05 to 0.5 μm and 20 to 70 μm, respectively.
However, both the above-described proposals aim to scatter light in a wide angle range. The irregular shape of the surface has a minute period and the surface profile has steep angle components. Consequently, there is a problem that the entire screen of a display apparatus appears whitish brown, that is, the contrast is decreased.
One approach to solve this problem is to increase the period of the irregular shape of the surface. However, if the period is increased in this manner, it becomes impossible to prevent reflection. That is, the contrast and the antiglare property are incompatible properties and it is difficult to satisfy these two properties at the same time.
Also, in some cases, front surface plates for the purpose of providing mechanical, thermal, and weathering protections and a design function are arranged on the front surface (the viewer's side) of, for example, liquid crystal displays, organic EL displays, and other display apparatuses. In such cases, when a rear surface (display apparatus side) of a front surface plate is flat and if, for example, the front surface plate is deflected and comes close to the display apparatus, a problem of occurrence of Newton rings occurs.
Furthermore, in the cases where another rear surface member is arranged at the rear surface side of a display apparatus, problems of deflection of members become severe, resulting in the problem of the occurrence of Newton rings. This is because the space between the display apparatus and the rear side member is narrowed with a reduction in the thickness of the display apparatus, and in addition, the size of the display apparatus is increasing. A description will be made using a liquid crystal display as an example. For example, in a liquid crystal display, a diffusing plate that makes the illuminance of light emitted from a light source uniform in a plane, a lens film for controlling the viewing angle, and a polarization separation reflective film that polarizes and separates light for reuse, and the like are arranged as the rear surface members. However, a polarizing plate disposed at the rear surface side of a liquid crystal panel and in front of these rear surface members usually has a flat surface profile (center-line mean roughness Ra=less than 0.03 μm, and root-mean-square slope RΔq=less than 0.01). Thus, occurrence of Newton rings has been a problem in thin liquid crystal displays.
Consequently, an optical film that can suppress occurrence of such Newton rings has been desired.
Accordingly, it is desirable to provide an optical film and a method for manufacturing the same, an antiglare film, a polarizer with an optical layer, and a display apparatus that can achieve both good contrast and antiglare property.
Furthermore, it is desirable to provide an optical film and a method for manufacturing the same, an antiglare film, a polarizer with an optical layer, and a display apparatus that can achieve both good antiglare property and image clarity and that can also suppress occurrence of Newton rings.